Hydrazodicarbonamide(HDCA) is a useful compound as a raw material for preparing azodicarbonamide which is widely used as a foaming agent. As shown in the following reaction Equation 1, azodicarbonamide(2) can be obtained by oxidation of hydrazodicarbonamide (1) with proper oxidation agent.

The conventional methods for preparing the hydrazodicarbonamide includes methods of (i) using hydrazine as a starting material, (ii) direct synthesis from urea, (iii) obtaining semicarbazide using urea, and then converting the obtained semicarbazide to hydrazodicarbonamide, and (iv) using biuret as starting material.
In the method of using hydrazine as a starting material (Reaction Equation 2), hydrazodicarbonamide is produced by reacting 1 mol of hydrazine(3) with 2 mol of urea(4),

The above-identified reaction has a merit in that the process is simple, but it has drawbacks in that the starting material, hydrazine is difficult to synthesis and expensive. The representative methods for preparing hydrazine includes Raschig process and method of using ketazine. However, there are also some problems in that hydrazine obtained by these methods needs concentration process and hydrolysis process. Therefore, the costs for energy and for utility are too high and accordingly the production cost is increasing. Further, hydrazine can also be prepared by the urea process which reacts urea with sodium hypochlorite and sodium hydroxide. But, this method needs excess of sodium hydroxide, and the cost to remove sodium carbonate by-product is very high, and many chemicals are required to remove the by-product. Thus, this method is esteemed as uneconomical and environmentally undesirable.
Following Equation 3 represents the direct synthetic method of hydrazodicarbonamide using urea. As shown in the Equation 3, the reaction of 3 mol of urea with 4 mol of sodium hydroxide and 1 mol of chlorine produces 1 mol of hydrazodicarbonamide. But, this method also is improper because the production cost is high due to the requirement of excess reagents and the process is very complicated. And there is another important problem in that a lot of ammonia are formed as by-product, which is environmentally undesirable.

Following Equation 4 shows another method of synthesizing hydrazodicarbonamide. The method comprises the steps of obtaining semicarbazide using urea, and subsequently converting the obtained semicarbazide to hydrazodicarbonamide. As shown in Equation 4, sodium monochlorourea salt is obtained by the reaction of urea with sodium hypochlorite, and the sodium monochlorourea salt reacts with excess ammonia in the presence of catalyst to produce the intermediate (semicarbazide), and then the obtained semicarbazide reacts with urea to produce the final product (hydrazodicarbonamide).

However this reaction also is economically inefficient because the reaction needs more than 500 times of excess ammonia per sodium monochlorourea salt, or semicarbazide is obtained by using expensive catalyst. There's another problem that entire process becomes longer because additional reaction of converting semicarbazide to hydrazodicarbonamide should be followed.
Following Equation 5 shows the method of synthesizing hydrazodicarbonamide using biuret (International Application PCT/KR00/00180). It comprises the steps of obtaining metal monohalobiuret salt by reacting biuret with metal hypohalogen (MOX), and subsequently reacting the obtained metal monohalobiuret with ammonia to obtain hydrazodicarbonamide.

However, the above method of producing hydrazodicarbonamide using biuret as a starting material has problems in that the whole process is uneconomic and environmentally undesirable because the biuret used as the starting material is very expensive or it contains a lot of impurities, and the reaction of biuret with ammonia to synthesize hydrazodicarbonamide needs additional ammonia.